Braking systems for wheelbarrows are known in the art. U.S. Pat. No. 2,716,031 to Roessler, for example, discloses a hand operated brake for a wheelbarrow having a pivoting hand lever connected by an adjustable length rod assembly to a pivoting arcuate brake shoe. Pivot of the hand lever by a user of the wheelbarrow causes pivot of the shoe into contact with an inner cylindrical surface of the wheel of the brake. This type of braking system in which an arcuate shoe contacts an inner cylindrical surface of a rotating member is typically referred to as a drum brake system.
A wheelbarrow having another type of braking system known as a disc brake system is disclosed in U.S. Pat. No. 5,690,191 to Burbank. The Burbank reference discloses a brake disc supported on fastened spacers by a vertical surface of a tire rim and a U-shaped caliper which positions brake pads on opposing sides of the brake disc. An actuating cable secured to one of the pads extends in a first pass between the brake pads and is returned in a second pass through aligned openings in the pads. Bushings are located in the brake pad openings to facilitate passage of the cable. Actuation by a user of the wheelbarrow forces withdrawal of a portion of the cable in the first and second passes and pulls the pads towards one another.
The cable actuator system of Burbank fails to provide efficient transfer of the force applied to the cable into a braking force applied to the disc. The forced withdrawal of cable through the bend between the cable passes which is necessary for drawing the pads together generates frictional forces between the cable and the bushings. These frictional losses limit the effectiveness of the pulling force which is applied.
Furthermore, the teaching in Burbank of supporting the disc on fastened spacers from a vertical surface of the wheel fails to provide proper support for the disc. Support from the wheel rim in such a manner results in substantial runout wobble of the disc.
What is needed is an actuator for a disc type braking system for a wheelbarrow in which tension applied to a cable is efficiently converted into a braking force applied to the disc. The interacting cam members and cam grooves of the brake actuator of the present invention provides mechanical advantage and highly efficient conversion of the force applied to the cable into braking force applied to the disc. Furthermore, the actuator of the present invention has bidirectional operation providing for alternative application of the actuator in either a manual cable-applied/spring released braking system or an automatic spring applied/cable released system. A benefit of automatic braking is the ability to park the wheelbarrow on a slope without the need for blocking of the wheel. This allows for safe loading of the wheelbarrow with assurance that the wheelbarrow will not move when gravity forces overcome frictional forces acting on the wheelbarrow supports. Such a system also provides a useful safety feature in that the wheelbarrow would automatically brake in the event a user of the wheelbarrow were to unintentionally lose control over the wheelbarrow while operating the wheelbarrow.